Chemicals most responsible for the toxicity outside this school

Definition: Maleic anhydride is used to produce agricultural chemics, resins, dyes and pharmaceuticals. Maleic anhydride ican irritate the respiratory system and induce asthma, and has a more severe impact on children than on adults. EPA has no evidence that the chemical causes cancer in humans. Source: EPA, CalEPA

Definition: Sulfuric acid is used in the production of fertilizers and explosives, in the purification of petroleum; in the pickling of metal; and in lead-acid batteries. Breathing sulfuric acid can result in tooth erosion and respiratory tract irritation. Exposures to large quantities at work can increase the incidence of cancers of the larynx, though such workers are often exposed to other chemicals, too. The International Agency for Research on Cancer says occupatonal exposure to inorganic acid mists can cause cancer, but pure sulfuric acid has not been classified. Source: IARC

Definition: Manganese is used to produce pesticides, batteries and other industrial products. Although trace elements are found in food and are considered essential for good health, overexposure for long periods can cause mental and emotional disturbances and slow and clumsy body movements -- a disease of the brain called manganism. Children are more vulnerable to such exposures than adults. EPA says that it cannot be determined if there is a link between manganese and cancer.

Definition: Diisocyanates are a group compounds used to manufacture foams, fibers, insulation, paints and varnishes, particularly in the automobile industry. Workers exposed to diisocyanates may develop serious or fatal respiratory diseases, including asthma, says the National Institute for Occupational Safety and Health. The World Health Organization has recommended that diisocyanates be treated as a potential human carcinogen.

Definition: Chromium is present in the environment in several different forms, some harmless and some harmful. Chromium 3 is an essential nutrient that helps the body process sugars, proteins and fats. Chromium 6, produced by industrial processes, can in high doses cause convulsions, kidney and liver damage, and even death. The World Health Organization, EPA and the U.S. Department of Health and Human Services have concluded that chromium 6 can cause cancer in humans.

Sources: U.S. Environmental Protection Agency, University of Massachusetts at Amherst Political Economy Research Institute

* Chemicals most responsible for the toxicity outside this school may not add up to 100% because only the top chemicals are listed.

To report corrections and clarifications, contact the USA TODAY investigative team. For publication consideration in the newspaper, send comments to letters@usatoday.com. Include name, phone number, city and state for verification.

Guidelines:
You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. Read more.

QUESTIONS YOU MIGHT HAVE

What if my school ranks high? Should I be alarmed? What do I do next? Can I test the air myself? Get answers.